Disc recording/reproducing system

Abstract: A disc recording/reproducing system where recording/reproduced data rates change stepwise when spiral record tracks on a disc medium are divided in multiple zones in the radial direction and the disc is rotated and driven at a constant angular velocity or when a rotating and driving angular velocity changes stepwise for every zone, the disc recording/reproducing system is provided with a data rate control area provided at the boundary between a first and second zones on the disc medium for controlling the recording/reproduced data rate, a control area detecting means for detecting the data rate control area when continuously recording/reproducing data extending over the first and second zones and a frequency control means for controlling frequency of a recording/reproducing data extracting PLL or a recording reference frequency generating PLL when the data rate control area is detected.

Description: The present invention generally relates to a disc recording/reproducing system, and more particularly, to a disc recording/reproducing system for performing the formatting of a disc according to the MCAV (Modified Constant Angular Velocity) system or the MCLV (Modified Constant Linear Velocity) system. So far, the CAV (Constant Angular Velocity) system has been largely used for record formatting of a writable optical disc for such merits as easy rotating system control, etc. However, recording/reproducing of voluminous image data has been demanded in recent years and the MCAV system of which more large capacity increase is expected has been increasingly adopted. In the MCAV system, as illustrated in FIGURE 1, it has been intended to increase the recording capacity of the entire disc by dividing the recording surface of a disc 600 into several zones concentrically and increasing the number of sectors per track more at the outer zones than the inner zones. In FIGURE 1. the numeral 601 shows the n-th recording zone from the inside of the disc 600, and the numeral 602 shows the (n+1)-th recording zone that is one zone outside the n-th recording zone. As the disc rotation is regulated to be constant likewise the CAV system, the control of the rotating system is easy but there is such a problem that the data processor becomes complicated as a recording/reproduced data rate differs for every zone. The complication of a circuit at the recording side is not so serious problem, but the processing at the reproducing side would become complicated as it might become necessary to adjust reproduced signal waveform equalization in consonance with data rate changes and a change-over of a frequency in a data extracting PLL. Furthermore, there is such a problem that the high level of high-frequency processing technology is demanded at the outer zones as recording/reproduced data rate would become high at the outer recording zones. As a method for solving these problems, there is a disc recording/reproducing system adopting the MCLV system. In this system, the format on a disc medium is the same as the MCAV system but the revolution speed for each zone is variable and a recording/reproduced data rate is kept constant. In order to change the disc revolution speed, the rotating control would become somewhat complicated but as the disc revolution speed has been fixed for each zone, the control of the rotating system is relatively easy when compared with the CLV system which requires the control of the rotation system while extracting a data rate. Here, it is the principal use of a writable optical disc which is so far available to handle program data and graphics data which are used by computers, etc. Therefore, it is important for such a disc to be able to record/reproduce data at higher speed and more positively. However, pursuant to the advance of image/audio compression technology in recent years, a required data storage capacity has been reduced and it has become possible to realize a digital video disc that is capable of recording/reproducing motion pictures and audio data as digital data on an optical disc. When considering such uses as described above, not only the possibility for recording/reproduction at high speed is required but also a real time property for constant recording/reproduction of required data will become important. The MCLV system has sufficient merits as a system under which the data processing and rotating system control are relatively easy and it is possible to achieve a large capacity. However, the MCLV system has a problem for uses to record/reproduce motion picture data, etc. That is, there is no problem in recording/reproduction within one zone, but when recording/reproducing data continuously extending over multiple zones, there is such a problem that a data rate abruptly changes because a disc rotation cannot be changed quickly corresponding to transitions between record zones. FIGURE 2 is a time chart showing a relationship between the disc revolution speed and data rates in the MCLV system. The disc revolution speed represented by the graph 700 cannot drop quickly, but it drops gently when the tracking operation of zones moves from the n-th record zone 601 to the (n+1)-th record zone 602. On the other hand, a reproduced data rate 701 becomes high temporarily when the tracking of record zones moves from the n-th record zone to the (n+1)-th record zone. Therefore, the data extracting PLL at the reproducing side cannot follow the quick change of the data rate. Also the reproduction processing cannot be performed until the data rate frequency enters into the PLL pull-in range. So, there is such a problem that the reproduction processing is suspended until the disc rotation is stabilized and required data could not be reproduced constantly. There is a method to compensate data that are lack during the suspension by storing reproduced data proportional to the suspension of the processing in a buffer memory in advance before a tracking operation moves to another record zone. However, this method requires a memory having a voluminous capacity for storing data for several tracks as it becomes necessary to make a retracing to the first sector of a zone after the disc rotation is stabilized. Furthermore, the complicated recording/reproduction processing is inevitable. As described above, in the conventional MCLV system, there is such a problem that a sufficient measure could not be taken for a real time property required for realizing digital video disc, etc., in the data processing when the tracking of record zones moves from zone to zone. As described above, according to the conventional MCLV system, there is also such a problem that when data are continuously recorded/reproduced extending over the data record zones, a data rate changes abruptly and the data extracting PLL cannot follow the abrupt change of data rates and the reproduction processing has to be suspended temporarily until the disc rotation is stabilized and thus, the real time property is impaired. It is, therefore, an object of the present invention to provide a disc recording/reproducing system which makes it possible to reproduce data continuously without suspending the data processing even in the MCLV system by eliminating such defects as described above. In order to achieve the object described above, the invention provides a data recording/reproducing disc for use in a disc recording/reproducing system in which recording/reproduced data rates change stepwise when spiral tracks on a disc medium are divided in multiple zones in the radial direction and the disc is rotated and driven at a constant angular velocity or in which the rotating and driving angular velocity changes stepwise for every zone, characterised in that the disc comprises: an unrecorded data area provided at a boundary between each zone and the next zone, enabling detecting means to detect the unrecorded data area, when continuously recording/reproducing data extends over said zones, and the frequency of a recording/reproducing data extracting phase locked loop or a recording reference frequency generating phase locked loop to be controlled when the unrecorded data area is detected. In a system using a data recording/reproducing disc as described above, when a recording/reproducing head, which traces a disc medium, passes through the data rate control sector provided on the boundary of the record zones, the frequency of the data extraction PLL is controlled when reproducing the data or the frequency of the recording reference frequency generating PLL are controlled when recording the data. Thus, respective PLLs can follow the abrupt change of data rates, preventing the suspension of data processing for a long time that is generated when the recording/reproducing data extends continuously over the record zones. Additional objects and advantages of the present invention will be apparent to persons skilled in the art from a study of the following description and the accompanying drawings, which are hereby incorporated in and constitute a part of this specification. For a better understandings of the present invention and many of the attendant advantages thereof, reference will now be made by way of example to the accompanying drawings, wherein: FIGURE 1 is an explanatory drawing of a disc recording format in a conventional MCLV system; FIGURE 2 is a drawing showing the relationship between the rotation speed of a disc and the data rate in a conventional MCLV system; FIGURE 3 is an explanatory diagram of a recording format of a disc according to one embodiment of the present invention; FIGURE 4 is explanatory diagrams for illustrating formats of data sectors 3 and 5, a rate control sector 4 and an ID data in the sectors in the embodiment shown in FIGURE 3; FIGURE 5 is a block diagram showing a reproduction side of the MCLV system according to a first embodiment shown in FIGURE 3; FIGURE 6 is a time chart for explaining the operating state of a data clock extracting section in the embodiment shown in FIGURE 3; and FIGURE 7 is a block diagram showing a reproduction side data clock extracting section of the MCAV system according to a second embodiment of the present invention. The present invention will be described in detail with reference to the FIGURES 3 through 7. Throughout the drawings, like or equivalent reference numerals or letters will be used to designate like or equivalent elements for simplicity of explanation. Referring now to FIGURES 3 and 4, a first embodiment of the disc recording/reproducing system according to the present invention will be described in detail. FIGURE 3 is an explanatory drawing of a recording format of discs according to the first embodiment of the present invention. A small circle 1 represents a light beam spot applied from an optical head (not shown) to the data carrying surface of a disc 2. The data carrying surface of the disc 2 are divided into concentric record zones, and further each record zone is divided into sectors. The light spot 1 traces, for instance, the last data sector 3 of the record zone No. 4, the data rate control sector 4 which is the data rate control area for the zone No. 4 and the first data sector 5 of the zone No. 5, in that order. FIGURE 4 is an explanatory drawing showing the data formats of the data sectors 3 and 5 and the rate control sector 4. The data sectors 3 and 5 are each composed of a preformat portion 6, a flag portion 7, a data portion 8 and a buffer portion 9. The preformat portion 6 is also composed of a sector mark 10, a PLL pull-in signal data 11, an address mark 12 and an ID data 13. The rate control sector 4 is actually formatted in the same manner as other sectors for a data recording/reproduction. The rate control sector 4 is composed of the preformat portion 6 and others, and the preformat portion 6 is composed of the sector mark 10, the PLL pull-in signal data 11 and the address mark 12 and the ID data 13. Here, the ID data 13 of the preformat portion 6 is used for distinguishing a normal data sector or a rate control sector. In case of the rate control sector 4, the zone No. 14 and the sector No. 16 are incremented according to respective positions of the zone and the sector likewise other data sectors. However the track No. 15, for instance, takes a fixed value not containing any "0" data, while other sectors are incremented from the inner sectors toward the outer sectors. Thus, the format can be easily identified only by the track No. 15. Further, as absolute positions of the sectors have been fixed, if the last data sector 3 of each zone has been recognized, it is easy to determine that the next sector is the rate control sector 4. FIGURE 5 is a block diagram showing a reproduction side data clock extracting section of the MCLV system according to one embodiment of the present invention. A signal read from an optical disc 301 by an optical head 300 is input to a data slicer 303 through a reproducing amplifier 302. The reproduced data is shaped by the data slicer 303 so as to be restored its original binary data, and then input to a rate control sector detector 304 and a PLL 305. In the rate control sector detector 304, a rate control sector is detected by detecting the ID data 13 in the preformat portion 6. The PLL 305 is composed of standard elements such as a phase comparator 306, an LPF 307, an adder 310 and a VCO 308 in addition to a frequency controller 309 for supplying a frequency control voltage to the adder 310. The frequency controller 309 controls the output frequency of a 1/S frequency divider 311 which divides the output frequency of the VCO 308 by S so as to the 1/S divided frequency is made equal to the output frequency of a 1/P frequency divider 312 which divides a reference clock (i.e., a data rate frequency). These frequencies from the 1/S frequency divider 311 and the 1/P frequency divider 312 are compared with each other by a frequency comparator 313. Then the count value of an up/down counter 314 is incremented or decremented according to the result of the comparison in the comparator 313. The count value of the up/down counter 314 is modified into a pulse width modulation (PWM) signal. The PWM signal is then supplied to the VCO 308 in a form of voltage signal through an LPF 316 and the adder 310. However, the frequency control is carried out only when the optical disc 301 is kept in the stopped state or when the data rate control sector detector 304 has detected a data rate control sector. When the optical disc 301 is kept in the stopped state, the outputs of the 1/S frequency divider 311 and the 1/P frequency divider 312 are selected to the same divided frequency so as that the oscillation frequency of the VCO 308 is controlled to approach the data rate frequency of a reference clock. In the ordinary reproducing operation, a selector 317 selects a status restoring circuit 318. Therefore, the control loop becomes the closed state in which a fixed voltage is input to the adder 310. FIGURE 6 is a time chart for explaining the operation of the data clock extracting section when the optical head 300 traces the record tracks from the zone No. 4 to the zone No. 5 in this embodiment. When the rate control sector detector 304 detects a rate control sector, the selector 317 selects the frequency comparator 313 so as to form a frequency control loop (FIGURE 6(a)). At this time, the value S of the 1/S frequency divider 311 takes a value the same as the number of sectors in the zone No. 5, while the value P of the 1/P frequency divider 312 takes a value the same as the number of sectors in the zone No. 4. As a result, the oscillation frequency of the VCO 308 increases so that the oscillation frequency of the PLL 305 approaches a reproduced data rate when the zone No. 5 is reproduced at the same disc revolution speed as the zone No. 4. After completed the frequency loop control, the status restoring operation starts. The status restoring circuit 318 restores the output value of the U/D counter 314 that was incremented or decremented in a loop control range [a] (see FIGURE 6) to the output value of the U/D counter 314 obtained through the frequency adjustment operation during the state that the optical disc 301 is kept in the stopped state. In this case, the output value is not restored at a stroke, but is restored in consonance with the change of the rotation of the optical disc 301, gradually for a long range [b] as illustrated in FIGURE 6. In this embodiment, as the oscillation frequency is forcibly changed in consonance with the change of the data rate, it becomes possible for the PLL 305 to surely read data from the first sector of a succeeding zone to which the reading operation has forwarded. FIGURE 7 is a block diagram showing a second embodiment of the reproduction side data extracting section of the MCAV system according to the present invention. In FIGURE 7, reference numerals used in the first embodiment, as shown in FIGURE 5, will be used to designate the equivalent elements. A signal read from an optical disc 301 by an optical head 300 is input to a data slicer 303 through a reproducing amplifier 302. The reproduced data is shaped in the data slicer 303 so as to be restored its original binary data, and then input to a rate control sector detector 304 and a PLL 305. In the rate control sector detector 304, a rate control sector is detected by detecting the ID data 13 in the preformat portion 6 (see FIGURE 4). The PLL 305 is composed of standard elements such as a phase comparator 306, an LPF 307, an adder 310 and a VCO 308 in addition to a frequency controller 309 for supplying a frequency control voltage to the adder 310. The frequency controller 320 controls the output frequency of a 1/S frequency divider 311 which divides the output frequency of the VCO 308 by S so as to the 1/S divided frequency is made equal to the output frequency of a 1/P frequency divider 312 which divides a reference clock (i.e., a data rate frequency). These frequencies from the 1/S frequency divider 311 and the 1/P frequency divider 312 are compared with each other by a frequency comparator 313. Then the count value of an up/down counter 314 is incremented or decremented according to the result of the comparison in the comparator 313. The count value of the up/down counter 314 is modified into a pulse width modulation (PWM) signal. The PWM signal is then supplied to the VCO 308 through an LPF 316 and the adder 310. However, the frequency control is carried out only when the optical disc 301 is kept in the stopped state or when the rate control sector detector 304 has detected a rate control sector. When the optical disc 301 is kept in the stopped state, the outputs of the 1/S frequency divider 311 and the 1/P frequency divider 312 are selected to the same divided frequency so as that the oscillation frequency of the VCO 308 is controlled to approach the data rate frequency of a reference clock. Although in the MCAV system the rotation speed of the disc 301 does not change, it is necessary to make the PLL 305 follow a data rate which changes for every transition of the tracking from zone to zone. Therefore, the frequency loop is controlled when the rate control sector detector 304 detects a rate control sector. In the second embodiment, as the frequency loop is controlled whenever a rate control sector is detected by the rate control sector detector 304 and the PLL follows a data rate which changes for every transition of tracking from zone to zone on the record carrying surface of the disc 301, it becomes possible to positively extract the reference clock in the MCLV system. Further, the first and second embodiments as described above are applied to the reproduction side, but they are also applicable to a recording side. At a recording side, it is not necessary to extract a reference clock. However in the MCAV system it is necessary, for instance, to change a recording data rate for every zone. When the rate control sector detector 304 detects a rate control sector, it is possible to control the operating frequency of the recording reference frequency generating PLL which decides a recording data rate. As described above, the present invention can provide an extremely preferable disc recording/reproducing system. That is, according to the present invention, even when data are continuously recorded/reproduced extending over some number of record zones, the data extraction PLL operation in the reproducing operation and the frequency in the recording reference frequency generating PLL operation in the recording operation are able to follow even the abrupt change of the data rate by controlling the frequency in each PLL operation, when the recording/reproducing head traces the data rate control area provided on the boundary between the record zones. Therefore, it is not necessary to suspend the recording/reproducing processing for a long hour. Thus, when only a relatively small buffer memory is provided, a continuous data recording/reproduction becomes possible and the recording/reproduction of such data as motion picture, etc. in which a real time property is regarded important can be achieved. It is intended that the present invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out the present invention, but that the present invention includes all embodiments falling within the scope of the appended claims. The foregoing description and the drawings are regarded by the applicant as including a variety of individually inventive concepts, some of which may lie partially or wholly outside the scope of some or all of the following claims. The fact that the applicant has chosen at the time of filing of the present application to restrict the claimed scope of protection in accordance with the following claims is not to be taken as a disclaimer or alternative inventive concepts that are included in the contents of the application and could be defined by claims differing in scope from the following claims, which different claims may be adopted subsequently during prosecution, for example, for the purposes of a divisional application.

Claims: A data recording/reproducing disc for use in a disc recording/reproducing system in which recording/reproduced data rates change stepwise when spiral tracks on a disc medium are divided in multiple zones in the radial direction and the disc is rotated and driven at a constant angular velocity or in which the rotating and driving angular velocity changes stepwise for every zone, characterised in that the disc comprises: an unrecorded data area provided at a boundary between each zone and the next zone, enabling detecting means to detect the unrecorded data area, when continuously recording/reproducing data extends over said zones, and the frequency of a recording/reproducing data extracting phase locked loop or a recording reference frequency generating phase locked loop to be controlled when the unrecorded data area is detected.

Inventors: ISHIZAWA YOSHIYUKI, ISHIZAWA, YOSHIYUKI, C/O INTELLECTUAL PROP. DIV.
Applicants: TOSHIBA KK, KABUSHIKI KAISHA TOSHIBA
Application year: 1994
Main classification: G11B7
IPC codes: G11B20, G11B7